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Scientific Proceedings (115). 



reagent was tried. This led to the discovery that there were two 

 factors in the precipitate, both of which were necessary to reac- 

 tivate the charcoal-treated infusion. One of these must be 

 carried down by adsorption in the original mercuric sulphate 

 precipitate, or else its solubility is influenced by the presence of 

 other substances, for it is not reprecipitated, to any extent, from 

 the mixture by the addition of mercuric sulphate. If the filtrate 

 from the first precipitation is tested for this factor, it is found to 

 be present in moderate concentration, although apparently less 

 than in the precipitate. 



There is some difficulty in making this separation quantita- 

 tive with mercuric sulphate, and a more convenient reagent was 

 found in silver sulphate and baryta. The original mercury 

 precipitate is freed from mercury by H 2 S, and after boiling out 

 the H 2 S and cooling, silver sulphate solution is added in slight 

 excess, and barium hydroxide solution to moderately alkaline 

 reaction to litmus. The precipitate, which is freed from silver 

 by H 2 S, contains histidine and considerable brown sticky material, 

 in addition to an active fraction which may be briefly referred to 

 as "X." If necessary, the second factor, or "Y," most of which 

 remains in the silver filtrate, may be removed more completely 

 by reprecipitating with silver sulphate and baryta. 



In several experiments it was found possible to precipitate 

 the histidine and the pigment with phosphotungstic acid, leaving 

 the active "X" in the filtrate. Evaporation to dryness after 

 removing the phosphotungstic acid, yielded a semi-crystalline 

 material, but also destroyed the activity of this fraction. These 

 experiments were made with a single solution of phosphotungstic 

 acid. With all the subsequent preparations of the reagent com- 

 plete loss of activity has resulted during the precipitation of the 

 crude "X" fraction, and neither the precipitate nor the filtrate 

 nor both together have given growth. It is possible that oxidation 

 may explain this change in properties, and further work must be 

 done in attempting the isolation of this factor. 



The silver sulphate filtrate, or "Y" fraction, does not give a 

 precipitate with phosphotungstic acid. Mercuric sulphate throws 

 down a rather abundant precipitate, composed probably of 

 tryptophane and tyrosine. The filtrate from this precipitate 



